Reddit reviews School Zone - Alphabet Stickers Workbook - 64 Pages, Ages 3 to 6, Preschool to Kindergarten, ABCs, Printing Letters, Matching, and More (School Zone Stuck on Learning® Book Series)

My son is also almost 3. He has been reading for about a year and is doing elementary school math. Here are some things we've tried:

For letter sounds, we had the Leapfrog alphabet bus which sings things like "A says ah."

For lowercase letters, we had the Hape lowercase letters wooden puzzle.

The Learning Journey Match It! - a series of spelling and reading puzzles. We didn't get into the ones that spelled entire words, but used something like this:

Melissa & Doug Self-Correcting Alphabet Wooden Puzzles With Storage Box (52 pcs) https://www.amazon.com/dp/B004PBNGEM/ref=cm_sw_r_cp_apa_i_QixdBb7S993V0

which helps teach the letter sounds and build phonemic awareness.

You mentioned sticker books; we did a lot of those. They're great for kids who can't write well yet. This one in particular was very nice:

Alphabet Stickers Workbook (Stuck on Learning) https://www.amazon.com/dp/1589477464/ref=cm_sw_r_cp_apa_i_MnxdBbQ1H1DB0

We also started this workbook: Phonics for Kindergarten, Grade K (Home Workbook) https://www.amazon.com/dp/1604187743/ref=cm_sw_r_cp_apa_i_isxdBb62MAF6D

But at that age (<2 yrs) we could only do a few from one page at a time; it was quite mentally taxing. Gel pens were all the rage with him at that time; hence the workbook.

Also we had the Lauri 60 Objects Foam Magnets. My son would make us spell out an object magnet's word on a Magna Doodle.

Once he could read reasonably well, he would just learn from workbooks on his own. But this kid may be a bit unusual in that he loves writing in workbooks. I would just find workbook pages with addition and subtraction problems correctly filled in. I've also bought books such as

How to Be Good at Math https://www.amazon.com/dp/1465435751/ref=cm_sw_r_cp_apa_i_pyxdBbZYH9V3D

and find him reading those from time to time.

Also my kid loved his calculator; first a cheap $1 one and now he has a TI-30XS that he plays with (this morning I saw him entering 60^2, 70^2 etc).

Another favorite toy is this clock:

Learning Resources Gear Clock, 4 Inch, Set of 6 https://www.amazon.com/dp/B0035OL4YE/ref=cm_sw_r_cp_apa_i_ACxdBbJ1EHBYX

(we only had one which was around $6).

Also Telly the Teaching Time Clock.

As for electronics, we do use some educational apps on a Kindle tablet and he loves math videos (such as Numberock songs) on YouTube. (He gets upset when I put Daniel Tiger on; he wants number videos).

For writing, we have the Leapfrog Mr. Pencil Scribble and Draw and some Kindle apps as well. His workbooks also have a lot of tracing activities.